Just 24 hours after a chemical spill was treated in Blackmans Swamp Creek, a second load of chemicals - believed to be paint or cleaning products - has been dumped into the waterway through a stormwater drain.

Orange City Council spokesperson Allan Reeder said the second incident confirmed council was treating the incidents as suspicious.

"The first pollution event might have been an accident or someone being careless, but two nights in a row looks more like a deliberate action," Mr Reeder said.

"Two nights in a row, at about the same time in the same location. Perhaps someone doing something at the end of the working day."

He appealed to anyone who may have information about people using paint or cleaning products to come forward and assist council.

Mr Reeder said containment booms put in place after the spill on Wednesday night had contained Thursday night's spill.

"Because of that quick response, any potential damage has been confined to about one hundred metres of Blackmans Swamp Creek," he said.

"A specialist trade waste company was at the scene [on Friday] using a 'peat moss-like' product that's scattered on the surface of the water.

"It acts very quickly to absorb contaminants that are floating on the surface. It can then be removed easily."

Council had been in contact with businesses in the area near the contamination's believed origin, who Mr Reeder said were concerned a backyard operator may have been "doing the wrong thing" instead of removing liquid waste themselves.

"If anyone knows anything that could help Council staff get to the bottom of this, please call the Council with that information," he said.